Feline infectious peritonitis (FIP) is a disease of both domestic and wild cats. The virus affects most of the internal organs of the animal and is almost always fatal. The virus is highly contagious, affecting kittens as well as adult cats.
The FIP virus was identified as a coronavirus by Horzinek and Osterhaus, Arch. Virol. 59:1(1979). FIP virus is related to transmissible gastroenteritis virus (TGEV) of pigs, enteric coronavirus of dogs and a respiratory coronavirus of man. There is also a feline enteric coronavirus (FECV) that replicates mainly in the intestine and causes only a mild diarrheal disease. Lutz, et al., J. Small Animal Pract. 27:108(1986).
Although it is known that FIP is caused by a coronavirus, the manner in which the infection is transmitted among cats and its pathogenesis are still poorly understood. The pathogenesis of the disease is very complex and studies indicate that host, viral and environmental factors play a role in the form and progression of the disease. Pedersen, et al., 34th Annual Symposium, Viral Diseases of Small Animals 7:1001(1985).
FIP can occur in two different forms: the wet or effusive form characterized by a fibrinous peritoneal exudate and the dry or parenchymatous form which is characterized by granulomatous inflammation of different organs and little or no exudate. Lutz, et al., supra.
Because there are other coronavirus infections of cats, for example, FECV, which are antigenically related to FIP virus, the pathogenesis of FIP has been difficult to characterize. As a result, serological tests for diagnosis of the disease have lacked specificity and have confused the interpretation of earlier studies. Pederson, Feline Practice 13:13(1983).
Until recently, protective active immunization against FIP was not possible. On the contrary, vaccinated cats were more susceptible to disease. Pedersen, et al., Am. J. Vet. Res. 44:229(1983); Weiss, et al., Comp. Immun. Microbiol. Infect. Dis. 4:175(1981); Weiss, et al., Am. J. Vet. Res. 41:663(1980).
Cats are infected by the oronasal route. FIP virus multiplies in epithelial cells of the upper respiratory tract and intestine. Clinically apparent FIP occurs after the virus crosses the mucosal barrier and causes an immune mediated disease. Lutz, et al., supra., Weiss, et al., Am. J. Vet. Res. 42:382(1981).
Stimulation of a nasal mucosal immune response is best done by intranasal administration of a vaccine. Bienenstock, et al., Immunology 41:249(1980); Murray, The Veterinary Record Nov. 10th:500(1973). Mucosal B-lymphocytes, stimulated to secrete anti-FIP virus IgA antibody, will also migrate to the gut mucosa and also confer local gut immunity. Murray, supra.
This invention is of a method for protecting feline animals against infection by FIP Virus which comprises intranasally administering an effective amount of a FIP Virus vaccine. This invention is also a FIP Virus vaccine comprising a temperature-sensitive (ts) FIP Virus. These and related aspects of the invention are fully described hereinbelow.
In a related aspect, this invention is a device for intranasally administering to a feline animal a non-pathogenic FIP Virus.